The objective of the proposed research is to determine how alterations in mitochondrial protein abundance and phosphorylation contribute to Type 2 Diabetes Mellitus (T2DM). Recent studies have linked mitochondrial dysfunction to insulin resistance. Dr. Alan Attie, co-sponsor of this proposal, uses genetics to understand the propensity to develop T2DM. Dr. David Pagliarini, sponsor of this proposal, focuses on the contribution of mitochondrial dysfunction to various diseases and understanding the basic science of mitochondrial biogenesis. Dr. Joshua Coon, the sponsor of my original application and a close collaborator on this proposal, is a leader in the development and application of mass spectrometry (MS) instrumentation for protein analysis. Having transition from the Coon group to start a second post-doc in the Pagliarini lab, I am continuing this project as the leading member of our interdisciplinary collaborative team. I have completed collection of an exhaustive quantitative proteomics dataset that constituted the bulk of my proposed research for this project in my original application. I observed highly reproducible alterations in protein abundance and phosphorylation in liver mitochondria in a cohort of over forty mice, which are either susceptible (B6) or resistant (BTBR) to developing T2DM when made obese. I am currently using this proteomics screen as preliminary data for hypotheses-driven targeted biological investigation. The rationale for the proposed research is that determining how phosphorylation modulates redox-regulatory proteins in obesity will open new avenues for developing therapeutic interventions for type 2 diabetes. The co-sponsoring environment will help facilitate my goal of starting an independent academic laboratory focused on utilizing proteomics and targeted biology to study redox signaling in metabolic disease. I will employ both biochemical, cell biology, and targeted proteomic approaches to carrying out the following Aims: Aim 1. Determine how the obesity-induced phosphorylation of the selenocysteine-specific elongation factor (Eefsec) regulates the production of redox-regulatory selenoproteins. I will test the hypothesis that enhanced obesity-induced phosphorylation of the non-mitochondrial isoform of Eefsec in diabetes- resistant B6 mice attenuates the production of inflammatory secreted selenoproteins without decreasing levels of key mitochondrial antioxidants, which are regulated by a mitochondrial-localized Eefsec isoform. Aim 2. Elucidate the role of obesity-induced phosphorylation of mitochondrial redox enzymes in regulating the abundance of bioactive lipophilic aldehydes. I will test the hypothesis that obesity-induced phosphorylation of dehydrogenase/reductase SDR family member 4 (Dhrs4) alters the levels of retinoid metabolites in diabetic BTBR mice through regulating the enzyme's retinal reducing activity. A parallel hypothesis I will test is that induction of aldehyde dehydrogenase 3A2 (Aldh3a2) expression and phosphorylation is a compensatory response in obesity for detoxifying reactive lipid-peroxidation products.